This invention relates to a combinatorial weighing system and, more particularly, to a combinatorial weighing system arranged so that a combinatorial weighing apparatus can be used with either a master-type packing machine or a slave-type packing machine by effecting a changeover between processing modes.
A combinatorial weighing apparatus now in practical use includes a plurality of weighing machines having respective weight sensors for weighing articles introduced into corresponding weighing hoppers, a multiplexer, an AD converter and a calculation control unit constituted by a microcomputer or the like which receives the measured weight values from the weighing machines through the AD converter and multiplexer. Under the control of a program stored in an internal memory, the calculation control unit generates combination patterns, each of which represents a different combination of the received weight values, and calculates the total weight of each combination. The calculation control unit compares each total weight value with signals from setting units which are used for setting a target weight value and allowable weight limits, selects a combination (referred to as the "optimum combination") the total weight value of which is equal to the set target weight or closest to the set target weight within the allowable weight limits, and causes the weighing hoppers of those weighing machines that have provided the weight values belonging to the optimum combination to discharge their articles.
The articles discharged from the combinatorial weighing apparatus are delivered to a nearby packing machine for packing the articles in a prescribed manner. As mentioned above, these articles are discharged from weighing machines selected on the basis of the optimum combination obtained through calculations for combinatorial weighing. In packing the discharged articles, there are instances where the operating conditions for packing may be satisfied on the packing machine side, while the conditions for discharging the articles are not satisfied on the side of the combinatorial weighing apparatus, as when the weighing apparatus has not been supplied with articles or is incapable of obtaining a combination within the allowable limits. In such case the packing machine continues to run and perform a packing operation on the assumption that articles are being discharged from the weighing apparatus, with the result that empty packages are sealed and discharged from the packing machine. This lowers the efficiency of the overall system. Accordingly, the usual practice is to control the combinatorial weighing apparatus and the packing machine in tandem in such a manner that the two may run efficiently in an operatively associated manner.
In order to achieve such control of the weighing apparatus and packing machine, two packing machine configurations are available, as illustrated in Figs. 3(a) and (b).
FIG. 3(a) illustrates a master-type packing machine which, in effect, controls the combinatorial weighing apparatus by supplying it with a timing signal each time articles are packed. The timing signal acts as a combinatorial weighing start signal to which the combinatorial apparatus responds by starting a combinatorial weighing operation.
FIG. 3(b) depicts a slave-type packing machine which the combinatorial weighing apparatus supplies with a discharge signal each time articles are weighed out, the signal acting as a packing start signal. The combinatorial weighing apparatus thus controls the packing machine, which is adapted to produce a signal indicating that conditions for starting packing are satisfied.
A disadvantage with this prior-art arrangement is that combinatorial weighing apparatus having different constructions must be used depending upon which of the two packing machines is adopted. The end result is a facility of high cost.